Scientists rewind aging clock in cells of cloned cows, study says

April 27, 2000
Web posted at: 2:50 p.m. EDT (1850 GMT)

From staff and wire reports

ATLANTA -- Scientists announced Thursday that a new cloning technique appears to rewind the aging clock in cow cells, and they have produced six calves through the process that show signs of being younger than their actual chronological ages.

"What we have shown for the very first time is the cloning procedure is actually reversing the aging process. In fact, it turns out that these cells are actually younger than their chronological age," said study leader Dr. Robert Lanza of Advanced Cell Technology, Inc.

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The six heifers were cloned from cells taken from a 45-day-old calf fetus. Researchers grew the fetal cells until they neared the end of their life span, then put those cells back into eggs, which they allowed to develop into calves.

The study, published in the journal Science, measured a tiny part of the calves' chromosomes called telomeres. These are little caps on the ends of the chromosomes that carry the genetic blueprint inside cells. Telomeres shorten as cells divide and grow older. A cell dies once the telomeres are frayed beyond repair.

The study authors found the telomeres in the cloned cows were much longer than those in normal cows of the same age, and in many cases they were longer than telomeres in newborn calves.

"What we showed in this paper is this clock gets reset. It gets wound back up," said Dr. Michael West, president and chief executive officer of the Worcester, Massachusetts-based company. "It remains to be determined whether this would extend the life of the animal."

These findings are surprising because the first cloned mammal, Dolly the sheep, appears to be older than her chronological age. Cloned in 1997 from an adult cell, Dolly's telomeres were shorter than normal at birth; they were the same length as those of the 6-year-old ewe from which she was cloned.

Researchers hope they may one day be able to use this cloning technology to develop treatments for human ailments. The authors speculate that cells could be used to grow replacement organs -- a new heart or liver for transplantation -- or tissues that could halt degenerative disease such as Alzheimer's, Parkinson's and diabetes.

"So what's exciting is, if we can reset the telomere program then the cells could grow longer and we could get enough cells to do the kind of therapeutics that I think people would like to see," said Douglas Wallace, director of the Center for Molecular Medicine at Emory University.

But there are a number of competing theories on why people and animals age, and scientists say it's not clear that the cloned calves will live longer. They point out that life span is determined by a number of factors and telomere length is just one.

"We can make no predictions on the life span of these calves and obviously what needs to be done is have a lot of these calves and see if their mean life span is longer or shorter," Wallace said.

Advance Cell Technology researchers agree, but say that the youth of the calves' cells may put them in a better position to ward off the damage that comes with age. That ability could one day lead to physically and mentally healthier lives for people.

"We could take one young cell from a patient and make hundreds or thousands of young cells and put them back in the patient and give them back a young immune system or give them back young cartilage in their knees," West said.

Lanza's team is continuing its cloning research. He said they do not quite know how the cows became "younger," but genes that usually become less active as a cell grows older were especially active in these cows, suggesting these animals are younger than their biological age.

"When other cows the same age start to grow old and frail, their cells should be able to divide the same as a newborn calf's. They should be able to repair damage due to disease and aging and should live longer, healthier lives," Lanza said.

Medical Correspondent Rhonda Rowland and Reuters contributed to this report.

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Science Magazine
National Bioethics Advisory Commission
Executive Summary -- Cloning Human Beings
New Scientist Planet Science | Cloning Report: Everything you always wanted to know...
Scientific American: Explorations: Cloning Hits the Big Time: 9/2/97
Roslin Institute Online: Information on cloning and nuclear transfer

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